Combined countersink and counterbore attachment for twist drills



Oct. 26, 1954 w. F. WOLFF 2,692,519

COMBINED COUNTERSINK AND COUNTERBORE ATTACHMENT FOR TWIST DRILLS Filed March 18, 1953 INVENTOR ATTORNEYS Patented Oct. 26, 1954 TENT OFFICE COMEENED COUNTERSINK AND COUNTER- BORE ATTACHMENT FOR TWIST DRILLS 1 Claim. 1

This invention relates to tools and more particularly to a combined countersink and counterbore attachment for twist drills.

An object of this invention is to provide an attachment for twist drills whereby the hole formed by the drill may be formed either with a countersink recess or with a counterbore, the device including a gauge or that the recess or counterbore may be made to the desired depth.

Another object of this invention is to provide a combined countersink and counterbore attachment for twist drills which can be used with drills of various sizes.

A further object of this invention is to provide an attachment of this kind which is simple in construction and can be produced at small cost.

With the above and other objects in view, my invention consists in the arrangement, combination and details of construction disclosed in the A invention,

Figure 2 is a detailed side elevation of the device,

Figure 3 is a sectional view taken on the line 3-3 of Figure 2,

Figure 4 is a plan view, partly broken away and in section, of the inner side of one of the elements forming this device.

Referringto the drawing, the numeral II! designates generally a conventional twist drill, and the numeral II designates generally an attachment which is adjustably mounted on the drill I and is adapted to form either a countersink or a counterbore in the material which is being drilled by the drill I0.

The attachment II comprises a pair of plates I2 and I3 which are of like construction and are disposed on opposite sides of the drill IIl. These plates I2 and I3 are clamping plates and each plate is formed with a longitudinal channel It adapted to partly receive the drill I0 and hold the drill against rotary movement when clamped between the two plates I2 and I3.

The plate I2 has extending from one end thereof a countersink forming blade I5 and has extending from the opposite end thereof a counterbore forming blade I5. The blade I6 is formed with a projection I! on the inner side thereof which is adapted to engage in a fiuting I8 of the drill Ill, as shown in Figure 2. Blade I5 is also provided with a projection or extension I9 at the point of the blade which is engageable in a fluting I8. The plates I2 and I3 are tightly clamped upon the drill III by means of clamping screws 20, and a set screw 2I is threaded through plate I2 and bears against the periphery of drill In order to provide a means whereby the depth of the countersink or counterbore may be regulated, plate I2 is provided with a pair of longitudinal openings 22 and 23 which open through opposite ends of the plate I2. The shank 24 of a gauge member generally indicated at 25 is adapted to engage in a selected one of the openings 22 or 23 and in the present instance the shank 24 is mounted in opening 23 and is secured against movement therein by means of a set screw 26.

The outer end of the gauge member 25 is formed with an eye 27 which is adapted to bear against the outer side of the work so that the operator may determine the exact depth of either the counterbore or the countersink.

In the use of this device, where it is desired to counterbore the work the tool is mounted after the manner disclosed in Figures 1 and 2, with the blades I6 of the counterbore element projecting in the direction of the cutting end of drill It. Gauge member 25 is set by adjustment of shank 24 in opening 23 so that the counterbore will be cut to the desired depth. Drill II) is operated in the normal manner and when blades I6 contact with the work the work is counterbored about the opening formed by the drill I0.

Where it is desired to form a countersink in the work, the tool is reversed so that the countersink blades I5 will project in the direction of the cutting end of drill Ill. Gauge member 25 is then reversed being placed in opening 22 so as to extend forwardly toward the countersink blade I5. As drill It! cuts into the work blades I5 will form a countersink for the fiat or tapered head of a screw or bolt when the drill enters the work to the depth of the countersink blades I5.

This attachment may be mounted on drill bits of varying sizes and can be readily adjusted along the length of the drills or drill bits so that a hole formed for a screw or bolt may be cut to the desired depth and the outer end of the hole formed either with a counterbore for receiving a washer, or a countersink for receiving the flat head of a screw.

I do not mean to confine myself to the exact details of construction herein disclosed. but claim 3 all variations falling within the purview of the appended claim.

What I claim is:

An attachment for twist drills comprising a pair of clamping plates engageable on opposite sides of a drill, each plate having a longitudinal channel on the inner face thereof in which a portion of the drill is adapted to engage, clamping screws for clamping said plates to the drill, a counterbore blade integral with and extending from one end of each plate, a countersink blade integral with and extending from the other end of each blade, and an inwardly extending projection carried by each blade engaging in a fluting References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 252,650 Cutter Jan. 24, 1882 277,859 Welles May 15, 1883 2,364,688 Bovee Dec. 12, 1944 

